This invention relates to a plug valve of a type useful in diverting or transferring flow of liquid through one piping circuit to another circuit without stopping the flow. More particularly, it pertains to a plug valve of such type which has an improved means for operating the plug thereof and for sealing the operating means against leakage.
A transfer or diverter valve is a type of plug valve used to switch the flow of liquid through one piping circuit to another piping circuit without interrupting or stopping the flow from the exit port of the valve, such as from one filtration or heat exchange system to another such system. For example, transfer valves are employed with duplex filtration systems for filtering lubricating oil supplied to compressors. When maintenance is to be performed on a filtration system which is in operation, the transfer valve is used to switch the flow from a circuit through the system in operation to a circuit through a standby system.
In known transfer valves which are now in general use, the operating joint between the valve operating shank or stem and the valve cover is most commonly sealed by an annular body or ring of fibrous or similar packing material, with the packing material being pressed against the stem by means of an adjustable gland. Typically, the packing ring is enlodged in an enlarged bore portion of a vertical opening formed in the valve cover; and the packing is forced downwardly into such bore and radially inwardly against the stem extending therethrough by turning a plurality of nuts extending through the gland and into the cover. The use of this type of packing ring around the stem increases the resistance to turning of the valve and requires adjustment to prevent leakage.
Diverter or transfer valves may also be equipped with means for lifting or jacking the valve plug from the valve bore and for lowering the plug back into place and securing the plug in the lowered position. One known embodiment of a jacking means comprises an oblong locking plate having a central opening therein to receive an upper end portion of the valve stem, and two bolt means which are threadably engaged in the valve cover for lifting and lowering the locking plate. This jacking assembly is separate from the aforementioned gland and packing assembly and is mounted coaxially with and above the gland assembly. To lift or jack the valve plug, the bolt means are turned to raise the locking plate against a handle which is connected to the upper end of the stem; and, thus, the valve plug is jacked from the valve bore as the locking plate bears upwardly against the handle. After the plug is jacked, the user turns the handle to change the flow of liquid through the valve from one piping circuit to the other. To lower and lock the plug into place, the bolt means are turned into the valve cover until the locking plate bears against an enlarged portion of the stem and thereafter for a prescribed number of turns to force the valve plug into the valve bore.
Another known construction of a diverter valve employs a similar jacking concept. However, instead of using bolts to lift a plate against the handle, a ring member is rigidly secured to the casing cover plate about the valve stem and above a packing gland of the aforementioned type, and a jacking nut is threadably engaged in a bore of the ring member and snugly about the stem. To lift or lower the plug, the jacking nut is rotated within the ring either upwardly against the handle or downwardly against an enlarged portion of the stem.
It will thus be appreciated that the construction of the conventional diverter valves is relatively complex, insofar as the valve operating or jacking assembly is separate from the gland and packing assembly. Also, in the conventional valves which employ a gland and packing assembly as described above, adjustment of the gland is required to assure that leakage about the stem is prevented.
It is an object of the present invention to eliminate such problems and to provide a plug valve having a jacking means wherein a gland is used to simultaneously serve as a jacking nut.
A further object of the present invention is to provide a plug valve having locknut means for preventing the valve plug from moving under the influence of high pressure and vibrations.
Still another object is the provision of a plug valve with foolproof means for preventing improper assembly of the valve.
The present invention also contemplates a plug valve providing fail-safe prevention of leakage through the valve plug jacking means when the valve plug is in an elevated or jacked position.